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H. 1. VAN DER BIJL. THERMIONIC AMPLIFIER AND RECTIHER.

APPLICATION FILED SEPT. I. 1915.

Patented. Aug. 1, 1916.

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. l I .1 I JBUEN'IDRIR JOHRRRES VAN nan RIdl'Ii, CI NEW YCRK, N. TX, RSSIGNOR, RY MESH E ASSIGN- IIENTS, TC WESTERN ELECTRIC COMJPRNY, INCORPORATED, R CORPORATION OF THERMICNIC' RIIPIIIIIER MID RECTIFIER.

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specification of Letters Patent.

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Application filed September I, 1915. Serial No. Mitt.

To all whom it may concern:

Be it known that I, Hnnnnrn JonANNns van DER BIJL, a subject of the King of Great Britain, residing at New York, in the county of New York and State of New York, have invented certain new and useful Improve ments in Thermionic Amplifiers and Rectifiers, of which the following is a full, clear, concise, and. exact description. This invention relates to detectors or amplifiers of the audion type having high current output, and its object is to render the filament of such tubes more durable.

In thermionic amplifiers and rectifiers of the audion type, the closeness ofthe input or grid electrode and filament to each other is important in determining the eficiency of operation. Furthermore, the distance of the output electrode from the filament and the amount of obstruction the input electrode or grid ofiers between the filament and output electrode are factors having a bearing on the current output of the audion. It has been found desirable for certain types of the amplifiers or rectifiers to have the filament in the same or approximately the same plane as the grid. It has, how-,

ever, been found that in such tubes, as shown in United States Patent 1,130,042, great difficulty the heated filament. This is caused by undue tension being applied to the filament by the supporting springs, unless the greatest care be exercised in manufacturing the tube. This invention afiords a means for doing away with these springs and substituting a means of support which is much easier to use, subjects the filament to less stress, and still permits bringing the filament and grid in substantially the same plane for the purpose cited above. This means consists of insulating material carried by the grid, and,

which insulating material supports the filament.

the supported filament; Fig. 2 is a detailed view of a modification.

In the drawing, 3 represents the usual containing vessel which is evacuated to a It two mica strips 7 in which strips are placed by undue tensions u is experienced due to breakage of- Referring to the drawing, Figure 1 shows a view in perspective of a vacuumtube with' suitable holes, through which is threaded the filament 8. Suitable electrode connections 9 are run through the base of the supporting member by means of which con tact may be madewith the various electrodes I in the tube.

' The arrangement of the elements above descrlbed permits the filament to be in substantially the same plane as the same time supplies a support for the filament which is easyto manipulate in manufacture and avoids the difiiculty caused on the said filament.

For-symmetry it is esirable that the same amount of filament surface shall be exposed freely to each of the members 4 of the output electrode. Care talcen to so thread the filament through the micastrips that there will be the same number of longitudinal sections 10 facing each of the plates 4. In some cases it is desirable to construct a tube of high voltage output. In this case it is found that the grid should be of a finer mesh and the distance between the grid and the filament should be smaller. It is not desirable, however, to have the filament strands too close together, and in such a case the modification shown in Fig. 2 may be used. In said modification, 11 shows the grid, 12 shows the mica strips threaded through in such a manner that the grid, and at IR i should, therefore, be 7 wherever the filament crosses a member of Y the grid, it. is separated and insulated therefrom by the mica strip. It is obvious that insulating material other than mica may be used without departing from'the spirit of this invention. It is also obvious that the mica strips or other insulating material thereby and a filament threaded through said insulating material, whereby the filament is supported by and brought into close proximity to said grid but insulated therefrom.

3. In a thermionic amplifier of the audion type, a grid; insulating material threaded into said grid and a filament threaded through said insulating material, whereby up the filament is supported byand brought into close proximity to said grid but is insulated therefrom.

4. In a thermionic amplifier of the audion E type, a grid; mica strips threaded into said grid and a filament threaded through said mica strips, whereby the filament is supported by and brought into close proximity to said grid but is insulated therefrom. 1'9 5. In a thermionic amplifier of the audion type, the combination of a grid; a double electrode facin each side of the g id; mica strips threade into grid and .a filament threaded through said mica strips in such a manner that an equal amount of filament surface is exposed to each plate surface.

In witness whereof, I hereunto subscribe my name this 27th day of August A. D.,

HENDKIK J OHANNES VAN DER BIJL. 

